Process for the removal of scale

ABSTRACT

A process for the removal and inhibition of scale in aqueous environments utilizing a composition having the formula: WHEREIN R is -CH2-CH2-COOX, X being a member selected from the class consisting of hydrogen, alkali metals, ammonium and substituted ammonium, and Y is selected from the class consisting of hydrogen and -CH2CH2-COOX, X being a member selected from the class consisting of hydrogen, alkali metals, ammonium and substituted ammonium.

United States Patent Bruson et a1.

Feb. 13, 1973 PROCESS FOR THE REMOVAL OF SCALE Inventors: Herman A.Bruson, Woodridge,

Conn.; Henry Gould, Houston, Tex.

Assignee: Milchem Incorporated, Houston,

Tex.

Filed: Sept. 23, 1971 Appl. No.2 183,278

US. Cl. ..252/82, 210/58, 252/180 ..C02b 5/06, C02b l/20 Field of Search..252/82, 87, 180; 210/58 References Cited UNITED STATES PATENTS Bruson..260/46 Croltz ..252/87 Gardner ..252/87 DePierri ..2lO/58 PrimaryExaminer-George F. Lesmes Assistant Examiner-J. P. BrammerAtt0rney-Bertram H. Mann et a].

[5 7 ABSTRACT A process for the removal and inhibition of scale inaqueous environments utilizing a composition having the formula:

26 Claims, No Drawings -CH CH COOX, X being a PROCESS FOR THE REMOVAL OFSCALE BACKGROUND OF THE INVENTION 1 Field of the invention The inventionrelates to a process for the inhibition and removal of scale formationon surfaces having a tendency to attract said scale by utilizingcompositions derived by cyanoethylation of acetone with acrylonitrile.

2. Description of the Prior Art The utilization of aqueous systems whichgenerally contain organic compounds, and the production and processingof hydrocarbons containing such impurities is impaired by theprecipitation of these impurities, resulting in the formation of solidmaterial, commonly referred to as scale. In the case of aqueousenvironments, the harmful effects of the formation of scale aregenerally confined to the reduction of the capacity of receptacles andconduits such as boilers, sea water evaporators and the like, which areemployed to store, treat and/or convey water. In the case of conduits,the the impedance of flow is a direct result of scale formation. Otherconsequences are not as obvious and will appear only after significantdamage has already occurred. For example, scale formed upon the surfacesof storage vessels and conveying lines for process water may breakloose. These large masses of deposit are entrained in and conveyed bythe water to damage and clog equipment through which water is passed,i.e., tubes, valves, filters, and screens. Additionally, these depositsmay appear in, and detract from, the final product which is derived fromthe process: for example, paper formed from an aqueous suspension ofpulp. Furthermore, when the contaminated water is involved in a heatexchange process, scale will be formed upon the heat exchange surfaceswhich are contacted by the water. This not only impairs heat transferefficiency, but will also reduce system flow.

The problem of scale formation is compounded in the production andprocessing of hydrocarbons generally caused by high levels of scaleprecipitation and growth. These levels may be supplied by process fluidsemployed in the production of the petroleum such as drilling fluids,water flooding chemicals employed to pressurize the productionformations, and the like. Inaddition, deposits leached and eroded fromproducing and adjacent formations such as limestone and from saltsolutions or brines which are admixed with crude hydrocarbons oftencontribute substantially to the formation and accumulation of scale. Thetendency of these contaminants to precipitate and form scale isaccelerated by changed physical conditions which attend withdrawal ofhydrocarbons from producing formations. Specifically, the extensionreduction of pressure which results from hydrocarbon withdrawalpermitsthe release of carbon dioxide with the consequent supersaturationof the brines or salt solutions contained by the hydrocarbons.

In addition to increased scale potential, petroleum production andprocessing are also characterized by a number of phases in which scaleformation is particularly troublesome. For example, the precipitation ofcontaminants is commonly experienced upon the withdrawal of thehydrocarbons from the producing formation and is accelerated byreduction in pressures and brine saturation. As a consequence, pluggingof the LII producing formation, well-strainers, valves, tubings, and thelike, is experienced from time to time. Scale is also formed uponsurface storage and processing equipment such as pipes, valves, heatingcoils and tubes, separators, scrubbers, heater-treaters, etc. In many ofthese processes scale reduces heat transfer and operating efficiency aswell as impeding flow and contributing to mechanical failures such asthe bending or clogging of pumps and valves.

Other crucial areas for the precipitation and accumulation of scale aresaline water evaporators, black liquor evaporators, boilers for theconversion of water to steam and evaporators in which raw sugar juice isconcentrated.

In the case of saline evaporators, the evaporation of sea or salinewater gives rise to the formation of scale deposits of low thermalconductivity on the heat transfer surfaces of the distillation plant.This causes a reduction in heat transfer coefficients which in turncauses deterioration in plant performance necessitating eventualshutdown of the plant for cleaning. In these heat transfer vessels,scale may be formed whenever scale-forming compounds are present in thefeed water. However, the type and composition of the scale may vary. Forexample, when evaporation of sea water takes place under reducedpressure at boiling temperatures below 148 F, the main scaling materialis calcium carbonate. However, at increased temperatures, it isprimarily magnesium hydroxide in the form of brucite. Nevertheless,calcium sulfate scale may be formed at all temperatures if the brineconcentration is sufficiently high.

When steam generation boilers and similar vessels are operated usingwater and heat transfer as a processing mechanism in, for example, blackliquor evaporation processes, a buildup of scale deposit formationresults in decreased overall efficiency. The

deposit formation tends to decrease heat transfer requiring an increasedheat input to accomplish the desired evaporation. These deposits, whichare very similar to those found in sea water evaporators and in lines,storage tanks and the like, and in hydrocarbon production, are primarilyorganic residues and soluble salts which can be removed by boil-outswith water.

In each of these areas of buildup, while calcium sulfate and calciumcarbonate are primary contributors to scale formation, other salts ofalkaline-earth metals and the aluminum silicates are also apparent.Magnesium carbonate, barium sulfate and aluminum silicate provided bysilts of the bentonitic, illitic and kaolinitic types often poseconsiderable scale problems in the aqueous and hydrocarbon environments.

It has been surprisingly discovered that organic pentacarboxylic andhexacarboxylic acids and water-soluble salts thereof prepared fromcyanoethylated acetone which is subsequently saponified possessextraordinary scale inhibition characteristics for aqueous environmentsand the like and may be used in a process to prevent and remove scaleaccumulation in environments having therein chemicals which have atendency to form said scale.

It is therefore an object of the present invention to provide a new andimproved scale inhibition process.

It is a further object of the present invention to provide a process forremoval of scale in aqueous environments, on the surfaces of heatexchange vessels, and the like.

Other objects and advantages of the present invention will be readilyapparent to those skilled in the art from a reading of the specificationand claims which follow.

SUMMARY OF THE INVENTION The present invention relates to a process forthe removal and inhibition of scale in aqueous environments utilizing acomposition having the formula:

wherein, R is CH CH -COOX, X being a member selected from the classconsisting of hydrogen, alkali metals, ammonium and substitutedammonium, and Y is selected from the class consisting of hydrogen and CHCH -COOX, X being a member selected from the class consisting ofhydrogen, alkali metals, ammonium and substituted ammonium.

DESCRIPTION OF THE PREFERRED EMBODIMENTS adjacent to the carbonyl group.Ketones which can be successfully obtained by utilizing about 350 gramsof acrylonitrile dissolved in about 120 grams of tertiary butyl alcohol,for each gram mole of acetone.

The reaction between acetone and acrylonitrile takes place readily attemperatures during the first half of the reaction about 25 C to about35 C, preferably at 30 C. During the second half of the reaction,temperatures between about 50 C and 65 C are utilized, preferably 60 C.The reaction has been found to be exothermal so that cooling, at leastduring the initial part of the reaction, may be advantageous in order tocontrol the vigor of the reaction and to prevent undesiredpolymerization or side reactions.

The reaction which occurs with five moles of acrylonitrile is:

1] alkaline CIl --C-Clh 5CH1=CII-CN catalyst ll (Nc-crig-o1Ii)lCcooH2omoN ll Similarly, acetone combines with 6 moles of acrylonitrile togive:

These cyanoethylation products are then saponified to the correspondingpolycarboxylic acid salts by reacting with, for example, an aqueousalkali metal hydroxide, such as a sodium or potassium hydroxide solutionto split off" ammonia as completely as possible, giving a water solublesalt. For example, in'the case of the preparation of the sodium salt thereaction would be as follows:

reacted in this manner include acetone, phenoxyacetone, cyano-acetone,ethoxy-acetone, acetophenone, p-methyl-acetophenone, acetyl-pcymene, andthe like. The polycarboxylic acid salt is then produced bysaponification or hydrolysis.

The polycarboxylic acids and water-soluble salts thereof used in thepresent invention may be prepared by reacting acetone in the presence ofa strongly basic alkaline catalyst with sufficient acrylonitrile tointroduce at least 5 and preferably 6 beta-cyanoethyl groups into theacetone molecule. Catalysts useful for this purpose are the alkalimetals and their oxides, hydroxides, alkoxides, and hydrides, as well asstrongly basic quaternary ammonium hydroxides and alkoxides. One orseveral of these materials may be suspended or dissolved in acetone orin a solution of acetone in an inert liquid which is less reactive thanthe reacting acetone, such as tertiary butyl alcohol. The quantity ofstrongly basic alkaline catalyst necessary for the reaction is betweenabout 0.5 and 2.0 percent of the combined weight of the reactants.Preferably, about 1.0 percent is utilized.

The amount of acrylonitrile necessary to react with acetone to produce 5to 6 beta-cyanoethyl groups on the acetone molecule will, of course,vary with the temperature and time of the reaction, as well as theselected solvent system and catalyst. However, good yields of 5 and 6beta-cyanoethylated acetone can be Any free alkali can be neutralizedwith strong acids such as sulfuric or hydrochloric acid since thepresence of minor amounts of alkali metal sulfates or chlorides in thedried finished product is tolerated. The solvent may also be evaporatedoff to leave behind the non-volatile salt of the polycarboxylic acid.

The water-soluble alkali metal salts of the polycarboxylic acidsprepared as above described can, if desired, contain more than onespecies of alkali metal cation. For example, in the case ofbeta-(hexacarboxyethyl)-acetone, four of the six carboxyl groups can beneutralized with sodium hydroxide. Of the remaining two carboxyl groups,one each can be neutralized with potassium hydroxide and lithiumhydroxide. For most scale treatment processes, the hexa-sodium salt ofhexacarboxyethylacetone, the penta-sodium salt ofpentacarboxyethylacetone, and mixtures thereof are preferred because oflow cost and efficiency. However, other water-soluble salts may also beused. For example, sodium, potassium, lithium, ammonium,ethanolammonium, diethanolammonium triethanolammonium,cyclohexylarnmonium,

morpholinium, piperidinium, hydrazinium, benzyl ammonium, and the like,may also be successfully used.

The amount of this material necessary to inhibit or remove scale willvary depending upon the particular application at hand. In ourlaboratory threshold test, described in detail in Example 11, we havefound that levels as low as 5 ppm of a 20 percent active aqueoussolution will be sufficient to significantly reduce the scale on surfaceof testing apparatuses. However, an increased treatment level may bedesirable when encountering extreme scale conditions. For example, whenusing the material in connection with, for example, floodwateroperations, treatment levels as high as 50 to 200 ppm may be desirableor necessary.

The process of inhibiting and removing scale of the present inventionutilizes the above described composition and comprises introducing thecomposition onto the surface area to be protected such as the internalmetallic tubing or lining of boilers, in the form of an aqueous solutionin an amount sufficient to inhibit or remove the scale and generallyprovide from about 5 ppm to about 200 ppm of the solution andmaintaining the composition in contact with the surfaces for a periodsufficient to inhibit the development of scale desposits thereon or toremove said scale deposit therefrom. It may be desirable to circulatethe composition through the treated system to provide sufficient contactof the composition with the surface to be protected. For example,underground strata surrounding a well bore can be treated by passing anaqueous solution of the composition into the strata by injection of thesolution down through the bore hole or production tubing, preferablyunder pressure.

The following examples further illustrate the preparation and use of ourcomposition and process.

EXAMPLE I The present example illustrates the preparation of the presentscale inhibition composition utilized in the present process. Into a oneliter 3-neck flask fitted with a stirrer, thermometer, funnel and refluxcondenser, was added a solution of 40 grams of tertiary butyl alcohol,29 grams acetone and grams of 5 percent potassium hydroxide in asolution of 95 percent tertiary butyl alcohol. To this solution wasadded dropwise a solution ,of 70 grams tertiary butyl alcohol and 170grams of acrylonitrile. Intermittent cooling was required because of anobserved vigorous exotherrn. of the acrylonitrile solution was added ata temperature of about C i 2 C. The next 20 percent of the acrylonitrilesolution was added at 30 C to 35 C. After one hour of acrylonitrileaddition, the reaction was aged for 1 hour. Ten grams of 5 percentpotassium hydroxide in 95 percent tertiary butyl alcohol was then addedas additional catalyst. The reaction temperature was then raised to 55C. The remainder of the acrylonitrile solution was then added over aperiod of about 75 minutes. During this period, additional heating wasrequired to maintain the reaction temperature at about 55 C 60 C. Thereaction batch was then permitted to age" for 2 1% hours at about 60 Cto 70 C.

The solvent and volatiles were distilled from the cyanoethylatedmaterial and the residue was hydrolyzed by adding 130 grams of sodiumhydroxide dissolved in 705 grams of water. The batch was heated toreflux at C at which point vigorous ammonia evolution was noted. Thereflux was continued for 3 hours until the ammonia in the overhead wasnegligible and the terminal pot temperature was between 105 C ll0 C.Reflux was then continued for 3 additional hours to complete thehydrolysis with intermittent distillate removal. Three additional hoursof reflux were required to insure the absence of nitrogen. The pH of thematerial was adjusted to about 9 with concentrated hydrochloric acid.

EXAMPLE II A standard calcium sulfate threshold performance test wasconducted utilizing a 20 percent solution of the sodium salt of thecomposition, made as in Example I in ppm levels ofO (blank), 5, l0, 15,2O, 50, 100, and 200, respectively. CC of a solution containing 20.9grams of Na SO and 200 grams NaCl per liter was prepared and added to 8ounce test bottles. To the test bottles was then added lOOCC of asolution containing 21.9 grams of CaCl ZH O and 200 grams of NaCl perliter. A clean glass microscope slide was then inserted into eachbottle. The bottles were capped and tightened to avoid moisture lossupon heating. The bottles were then placed in a preset 70 C oven forapproximately 18 hours. After this period, the bottles were removed andthe cells, slides and solution surface were examined for the presence ofcalcium sulfate scale. The test results were reported as scale," tracescale, or clean and is related to the ppm level of inhibitor insolution. The calcium sulfate threshold concentration of the testchemical is the concentration required to maintain a completely crystalfree test solution. The results of this test indicated that thecomposition utilized in the present process effectively prevented scaleat the 10 ppm concentration and was satisfactory at the 5 ppm level. Thefollowing table further illustrates the result of this test:

TABLE 2 Treatment PPM Observations Blank Scale on cell, slide andsurface of solution Compo. of Example I 5 Small crystal on surface ofsolution only l0 No scale l5 No scale 20 No scale 50 No scale l00 Noscale 200 No scale Although the invention has been described in terms ofspecified embodiments which are set forth in detail, it should beunderstood that this is by illustration only and that the invention isnot necessarily limited thereto, since alternative embodiments andoperating techniques will become apparent to those skilled in the art inview of the disclosure. Accordingly, modifications are contemplatedwhich can be made without de parting from the spirit of the describedinvention.

We claim:

1. A process for inhibiting the formation of scale on a surface incontact with an aqueous system containing chemicals having a tendency toform said scale which process comprises contacting said surface in aneffective scale removing amount with an aqueous solution of acomposition having the formula wherein R is -CH CH -COOX, X being amember selected from the class consisting of hydrogen, alkali metals,ammonium and substituted ammonium, and Y is selected from the classconsisting of hydrogen and CH CH -COOX, X being a member selected fromthe class consisting of hydrogen, alkali metals, ammonium andsubstituted ammonium.

2. The process of claim 1 wherein the scale inhibiting amount of saidcomposition is from about 5 ppm to about 200 ppm.

3. The process of Claim 1 wherein said aqueous system is a brine.

4. The process of Claim 1 wherein said aqueous system is water.

5. The process of Claim 1 wherein R is CH CH -COONa and Y is selectedfrom the class consisting of H and -CH CH COONa.

6. The process of claim 1 wherein R is CH CH -COOX, X being a memberselectef from the class consisting of hydrogen, alkali metals, ammonium,substituted ammonium, and mixtures thereof, and Y is selected from theclass consisting of hydrogen and CH -CH COOX, X being selected from theclass consisting of hydrogens, alkali metals, ammonium, substitutedammonium, and mixtures thereof.

7. The process of claim 1 wherein said surface is the internal metalliclining of a steam boiler.

8. The process of claim 1 wherein said surface is a subterraneanformation.

9. The process of claim 1 wherein said surface is the internal lining ofan evaporator.

10. The process of claim 1 wherein the scale is calcium carbonate.

11. The process of claim 1 wherein the scale is calcium sulfate.

12. The process of claim 1 wherein the scale is barium sulfate.

13. The process of claim 1 wherein the scale is aluminum silicate.

14. A process for the removal of scale selected from the classconsisting of alkaline earth metal salts and aluminum silicate on asurface in contact with an aqueous system containing chemicals formingsaid scale which process comprises contacting said surface in aneffective scale removing amount with an aqueous solution of acomposition having the formula wherein R is Cl-it,--CH -COOX, X being amember selected form the class consisting of hydrogen, alkali metals,ammonium and substituted ammonium, and Y is selected from the classconsisting of hydrogen and CH CH COOX, X being a member selected fromthe class consisting of hydrogen, alkali metals, ammonium andsubstituted ammonium.

15. The process of claim 14 wherein the scale removing amount is fromabout 5 ppm to about 2()( pm.

6. The process of claim 14 wherein sat aqueous system is a brine.

17. The process of claim 14 wherein said aqueous system is water.

18. The process of claim 14 wherein R is -CH CH COOX, X being a memberselected from the class consisting of hydrogen, alkali metals, ammonium,substituted ammonium and mixtures thereof, and Y is selected from theclass consisting of hydrogen and CH CH -COOX, X being selected from theclass consisting of hydrogen, alkali metals, ammonium, substitutedammonium, and mixtures thereof;

19. The process of claim 14 wherein said surface is the internalmetallic lining of a steam boiler.

20. The process of claim 14 wherein said surface is a subterraneanformation.

21. The process of claim 14 wherein said surface is the internal liningof an evaporator.

22. The process of claim 14 wherein the scale is calcium carbonate.

23. The process of claim 14 wherein the scale is calcium sulfate.

24. The process of claim 14 wherein the scale is barium sulfate.

25. The process of claim 14 wherein the scale is aluminum silicate.

26. The process of claim 14 wherein R is Cl-l CH COONa and Y is selectedfrom the class consisting of H and CH --CH -COONa.

1. A process for inhibiting the formation of scale on a surface incontact with an aqueous system containing chemicals having a tendency toform said scale which procesS comprises contacting said surface in aneffective scale removing amount with an aqueous solution of acomposition having the formula wherein R is -CH2-CH2-COOX, X being amember selected from the class consisting of hydrogen, alkali metals,ammonium and substituted ammonium, and Y is selected from the classconsisting of hydrogen and -CH2-CH2-COOX, X being a member selected fromthe class consisting of hydrogen, alkali metals, ammonium andsubstituted ammonium.
 2. The process of claim 1 wherein the scaleinhibiting amount of said composition is from about 5 ppm to about 200ppm.
 3. The process of Claim 1 wherein said aqueous system is a brine.4. The process of Claim 1 wherein said aqueous system is water.
 5. Theprocess of Claim 1 wherein R is -CH2-CH2-COONa and Y is selected fromthe class consisting of H and -CH2-CH2-COONa.
 6. The process of claim 1wherein R is -CH2-CH2-COOX, X being a member selectef from the classconsisting of hydrogen, alkali metals, ammonium, substituted ammonium,and mixtures thereof, and Y is selected from the class consisting ofhydrogen and -CH2-CH2-COOX, X being selected from the class consistingof hydrogens, alkali metals, ammonium, substituted ammonium, andmixtures thereof.
 7. The process of claim 1 wherein said surface is theinternal metallic lining of a steam boiler.
 8. The process of claim 1wherein said surface is a subterranean formation.
 9. The process ofclaim 1 wherein said surface is the internal lining of an evaporator.10. The process of claim 1 wherein the scale is calcium carbonate. 11.The process of claim 1 wherein the scale is calcium sulfate.
 12. Theprocess of claim 1 wherein the scale is barium sulfate.
 13. The processof claim 1 wherein the scale is aluminum silicate.
 14. A process for theremoval of scale selected from the class consisting of alkaline earthmetal salts and aluminum silicate on a surface in contact with anaqueous system containing chemicals forming said scale which processcomprises contacting said surface in an effective scale removing amountwith an aqueous solution of a composition having the formula wherein Ris -CH2-CH2-COOX, X being a member selected form the class consisting ofhydrogen, alkali metals, ammonium and substituted ammonium, and Y isselected from the class consisting of hydrogen and -CH2-CH2-COOX, Xbeing a member selected from the class consisting of hydrogen, alkalimetals, ammonium and substituted ammonium.
 15. The process of claim 14wherein the scale removing amount is from about 5 ppm to about 200 ppm.16. The process of claim 14 wherein said aqueous system is a brine. 17.The process of claim 14 wherein said aqueous system is water.
 18. Theprocess of claim 14 wherein R is -CH2-CH2-COOX, X being a memberselected from the class consisting of hydrogen, alkali metals, ammonium,substituted ammonium and mixtures thereof, and Y is selected from theclass consisting of hydrogen and -CH2-CH2-COOX, X being selected fromthe class consisting of hydrogen, alkali metals, ammonium, substitutedammonium, and mixtures thereof.
 19. The process of claim 14 wherein saidsurface is the internal metallic lining of a steam boiler.
 20. Theprocess of claim 14 wherein said surface is a subterranean formation.21. The process of claim 14 wherein said surface is the internal liningof an evaporator.
 22. The process of claim 14 wherein the scale iscalcium carbonate.
 23. The process of claim 14 wherein the scale iscalcium sulfate.
 24. The process of claim 14 wherein the scale is bariumsulfate.
 25. The process of claim 14 wherein the scale is aluminumsilicate.